The present invention relates to a skin prick test kit for the determination of the predisposition of an individual to develop marginal periodontitis. The invention also involves a method for the determination of such predisposition.
The most frequent disease that affects the attachment apparatus of the teeth or the periodontium is gingivitis. It is caused by our indigenous bacterial flora and is, for some individuals a first step towards marginal periodontitis. A shift towards more anaerobic bacteria in the bacterial plaque is thought to be the reason why gingivitis turns into marginal periodontitis. Despite the fact that almost all individuals suffer from gingivitis, there is no clear relation between the degree of gingivitis and development of marginal periodontitis. Epidemiological studies have, however, shown that between 5 and 10% of the adult population develop severe marginal periodontitis, while a moderate form affects 50 to 80%.
Progression of periodontitis is influenced by a multitude of modifying factors (Genco, RJ, Lxc3x6e H. The role of systemic conditions and disorders in periodontal disease. Periodontol 2000 1994; 2: 98-116). These can be divided into systemic factors which affect the entire dentition and local factors which affect a single tooth or tooth surface.
The teeth are attached to the alveolar bone through their roots. A thin layer of mineralized cementum is found along the surface of the roots. The cementum layer anchors collagen fibers which extend to the adjacent alveolar bone. The space, thus created between the root and the bone surfaces, is occupied mainly by collagen fibers and connective tissue cells (fibroblasts). The soft tissue, known as the periodontal membrane or ligament, is a highly specialized connective tissue. It has the capacity to form bone as well as cementum and can, provided the right conditions are given, form a new attachment apparatus in areas of the root where it has been lost to periodontal disease (Lindskog S, Lengheden A, Blomlxc3x6f L. Successive removal of periodontal tissues. Marginal healing without plaque control. J. Clin. Periodontol 1993; 20: 14-9).
Periodontal disease is, second to tooth decay, the most frequent oral disease. It is a progressive disease and affects, in its severe form, 5 to 10% of the population in industrialized countries, leading to partial or complete tooth loss. However, most adults have one or more teeth affected by the disease. The disease is, in its most common form known as marginal periodontitis. It is caused by accumulation of bacterial deposits on tooth surfaces along the gingival margins. These bacteria, predominantly anaerobic originate from the hosts indigenous oral microflora and elicit an inflammatory reaction in the gingiva which results in destruction of tooth-supporting tissues (periodontal membrane and alveolar bone). The destruction of tooth-supporting tissues results in a deepening of the space (periodontal pocket) between the root of the tooth and the gingiva. The disease progresses as bacteria migrate apically into the periodontal pocket, which deepens more and more as a result of the soft tissue inflammation. Unless adequate treatment is instigated, the tooth becomes mobile and will eventually fall out when enough tooth-supporting tissues have been destroyed.
Three theories on or models for progression of marginal periodontitis have been proposed (Socransky SS, Haffajee AD, Goodson J, Lindhe J. New concepts of destructive periodontal disease. J. Clin Periodontol 1984; 11: 21-32):
1. A slow continuous loss of attachment throughout life.
2. Random periods of attachment loss throughout life.
3. Localized attachment loss during certain periods in life.
There is reason to believe that all three theories are valid, each within a certain subpopulation of patients suffering from marginal periodontitis. The first theory/model applies to the majority of patients, 50 to 80% of the population, which show a moderate form of marginal periodontitis. The third theory/model applies to juvenile periodontitis which affects young patients and then most often only the first permanent molars. The second theory/model accounts for the 5 to 10% of the population which suffer from severe marginal periodontitis.
Within the group of patients suffering from severe marginal periodontitis and which lose periodontal attachment during random periods throughout life (theory/model 2 above) a large number of patients fail to respond to treatment (refractory patients). These patients have most probably a xe2x80x9cmulti-factorial genetic predispositionxe2x80x9d to develop severe marginal periodontitis.
This genetic predisposition has been suggested to lead to an inflammatory overreaction to marginal bacterial plaque which in turn causes destruction of the marginal periodontium.
The main object of the present invention is to provide new techniques residing in a screening test to identify within a given population individuals who have predisposition to develop marginal periodontitis.
Another object of the present invention is to provide a skin prick test kit for such determination of predisposed individuals.
Another object of the invention is to provide a method for the determination of such predisposition of individuals within a given population.
For these and other objects which will be clear from the following disclosure the invention provides for a skin prick test kit for the determination of the predisposition of an individual to develop marginal periodontitis, said kit comprising:
a) a first reagent containing a known quantity of a surface structure common to anaerobic Gram negative pathogens which is capable of triggering the inflammatory response associated with periodontitis and gingivitis;
b) a second reagent containing an agonist to said individual;
c) a negative control; and
d) instructions for the use of said kit.
It is preferred that said first reagent contains a structure selected from the non-polysaccharide entity of surface lipo- or proteoconjugates of such anaerobic Gram negative pathogens.
It is particularly preferred that said conjugate is a lipopolysaccharide, and in such conjugate it is particularly preferred that said entity is Lipid A or an equivalent thereof of same biological function.
In regard to the second reagent said agonist can be any substance capable of producing an inflammatory response on challenge of an individual subject to test. Although any agonist of such function can be used it is preferably selected from histamine, serotonin, prostaglandins, leukotrienes and bradykinin.
It is particularly preferred to use as an agonist histamine which is a conventional challenge substance used in testing immunologic reaction.
The invention also provides for a method for the determination of the predisposition of an individual to develop marginal periodontitis. In such a method the skin prick test is performed by challenging an individual subject to testing with a first reagent as defined above, evaluating the reaction of said challenge. In this method lack of reaction or generation of only a minor reaction indicates predisposition to develop a marginal periodontitis.
As will be shown below by experimental data patients refractory to treatment surprisingly present a reverse response, i.e. they do not respond as readily as healthy individuals with an inflammatory reaction to a given common Gram negative bacterial antigen, such as Lipid A. This impaired response could therefore lead to an unimpaired or uncontrolled growth of the marginal microflora, especially the anaerobic subgingival pathogens which, when they reach a critical volume, initiate a period of marginal attachment loss. The techniques presented by the present invention residing in the administration of a suitable antigen, such as Lipid A, thus has the potential of serving as a screening test for the early identification of individuals which have a predisposition to develop severe marginal periodontitis.
In regard to the first reagent any antigen or surface structure common to Gram negative bacterial periodontitis pathogens can be used in the test method according to the present invention. Such antigens are frequently part of surface conjugates of said pathogens, such as lipo- or proteopolysaccharides. Since the polysaccharide part of such conjugates has a structure varying with the type of bacterial strain involved, it is preferred to use the non-polysaccharide entity of such conjugates, said entity being unaltered regardless of bacterial strain.
With regard to the second reagent used in the present invention to confirm a positive reaction, it goes without saying that any agonist can be used for such purpose. Furthermore, the negative control for confirming negative reaction can be simply constituted by pyrogene free water.